AES San Francisco 2008Poster Session P20

P20 - Loudspeakers—Part 3

Saturday, October 4, 2:30 pm — 4:00 pmP20-1 Preliminary Results of Calculation of a Sound Field Distribution for the Design of a Sound Field Effector Using a 2-Way Loudspeaker Array with Pseudorandom Configuration—Yoshihiro Iijima, Musashi Institute of Technology - Tokyo, Japan; Kaoru Ashihara, Advanced Industrial Science and Technology - Tsukuba, Japan; Shogo Kiryu, Musashi Institute of Technology - Tokyo, JapanWe have been developing a loudspeaker array system that can control a sound field in real time for live concerts. In order to reduce the sidelobes and to improve the frequency range, a 2-way loudspeaker array with pseudorandom configuration is proposed. Software is being developed to determine the configuration. For now, the configuration is optimized for a focused sound. The software calculates the ratio between the sound pressure of the focus point and the average of the sound pressure around the focus. It was shown that the sidelobes can be reduced with a pseudorandom configuration.
Convention Paper 7616 (Purchase now)

P20-2 Design and Implementation of a Sound Field Effector Using a Loudspeaker Array—Seigo Hayashi, Tomoaki Tanno, Musashi Institute of Technology - Tokyo, Japan; Toru Kamekawa, Tokyo National University Arts and Music - Tokyo, Japan; Kaoru Ashihara, Advanced Industrial Science and Technology - Tokyo Japan; Shogo Kiryu, Musashi Institute of Technology - Tokyo, JapanWe have been developing an effector that uses a 128-channel two-way loudspeaker array system for live concerts. The system was designed to realize the change of the sound field within 10 ms. The variable delay circuits and the communication circuit between the hardware and the control computer are implemented in one FPGA. All of the delay data that have been calculated in advance are stored in the SDRAM that is mounted on the FPGA board, and only the simple command is sent from the control computer. The system can control up to four sound focuses independently.
Convention Paper 7617 (Purchase now)

P20-3 Wave Field Synthesis: Practical Implementation and Application to Sound Beam Digital Pointing—Paolo Peretti, Laura Romoli, Lorenzo Palestini, Stefania Cecchi, Francesco Piazza, Universita Politecnica delle Marche - Ancona, ItalyWave Field Synthesis (WFS) is a digital signal processing technique introduced to achieve an optimal acoustic sensation in a larger area than in traditional systems (Stereophony, Dolby Digital). It is based on a large number of loudspeakers and its real-time implementation needs the study of efficient solutions in order to limit the computational cost. To this end, in this paper we propose an approach based on a preprocessing of the driving function component, which does not depend on the audio streaming. Linear and circular geometries tests will be described and the application of this technique to digital pointing of the sound beam will be presented.
Convention Paper 7618 (Purchase now)

P20-4 Highly Focused Sound Beamforming Algorithm Using Loudspeaker Array System—Yoomi Hur, Seong Woo Kim, Yonsei University - Seoul, Korea; Young-cheol Park, Yonsei University - Wonju, Korea; Dae Hee Youn, Yonsei University - Seoul, KoreaThis paper presents a sound beamforming technique that can generate a highly focused sound beam using a loudspeaker array. For this purpose, we find the optimal weight that maximizes the contrast of sound power ratio between the target region and the other regions. However, there is a limitation to make the level of non-target region low with the directly derived weights, so the iterative pattern synthesis technique, which was introduced for antenna array, is investigated. Since it is assumed that there are imaginary signal powers in the non-target regions, the system makes efforts to further improve the contrast ratio iteratively. The performance of the proposed method was evaluated, and the results showed that it could generate highly focused sound beam than conventional method.
Convention Paper 7619 (Purchase now)

P20-5 Super-Directive Loudspeaker Array for the Generation of a Personal Sound Zone—Jung-Woo Choi, Youngtae Kim, Sangchul Ko, Jung-Ho Kim, Samsung Electronics Co. Ltd. - Gyeonggi-do, KoreaA sound manipulation technique is proposed for selectively enhancing a desired acoustic property in a zone of interest called personal sound zone. In order to create the personal sound zone in which a listener can experience high sound level, acoustic energy is focused on only a selected area. Recently, two performance measures indicating acoustic properties of the personal sound zone—acoustic brightness and contrast—were employed to optimize driving functions of a loudspeaker array. In this paper first some limitations of individual control method are presented, and then a novel control strategy is suggested such that advantages of both are combined in a single objective function. Precise control of a sound field with desired shape of energy distribution is made possible by introducing a continuous spatial weighting technique. The results are compared to those based on the least-square optimization technique.
Convention Paper 7620 (Purchase now)